Currently, there are two water-receiving trays disposed in an indoor unit of many air conditioners in North America, to adapt to a longitudinal arrangement and a transverse arrangement. As shown in FIG. 1, a heat exchanger 3 inside an indoor unit 1 generally is in the shape of A. A cusp of the heat exchanger is upwards in the case of the longitudinal arrangement and the cusp of the heat exchanger is leftwards or rightwards in the case of the transverse arrangement. In the transverse arrangement, the indoor unit defines a return-air inlet at a left side, and in some cases air may be blown to an air outlet 55 from left to right or blown from right to left. However, a water-receiving tray 2 at a lateral side is located below the heat exchanger, causing that a blowing direction is basically parallel to an arrangement direction of the water-receiving tray, in which case water in the water-receiving tray in a horizontal direction cannot be drained smoothly, and when a lot of water stores in the water-receiving tray, the wind may often blow the water in the water-receiving tray to move.